Phased slot antenna array with frustoconical reflector

ABSTRACT

An antenna for omnidirectional or directional transmission. The antenna comprises a central member for supporting at least one pair of spaced frustoconical reflector elements. The support member is slotted between the reflector elements to serve as an energy radiator. Energy is supplied to the radiator by connecting adjustable probes between the slots and a central conductor within the support member.

United States Patent Howard E. Griffith P. O. Box 547, West Monroe, La.71291 Appl. No. 849,969

Filed Aug. 14, 1969 Patented Sept. 14, 1971 lnventor PHASE!) SLOTANTENNA ARRAY WITH rnus'rocomcu. REFLECTOR 10 Claims, No Drawings us. c1343/171, 343/774, 343/884 rm 0! Search 343/773,

[56] References Cited UNITED STATES PATENTS 2,471,021 5/1949 Bradley2,631,237 3/1953 Sichak etal.

2,947,988 8/1960 Masters 2,971,193 2/1961 Siukola FOREIGN PATENTS 114,368 12/1941 Australia 649,944 2/1951 Great Britain PrimaryExaminer-Eli Lieberman Attorney-Cushman, Darby & Cushman ABSTRACT: Anantenna for omnidirectional or directional transmission. The antennacomprises a central member for supporting at least one pair of spacedfrustoconical reflector elements. The support member is slotted betweenthe reflector elements to serve as an energy radiator. Energy issupplied to the radiator by connecting adjustable probes between theslots and a central conductor within the support member.

PHASED SLOT ANTENNA ARRAY WITH FRUSTOCONICAL REFLECTOR A shortcoming ofconventional antennas for transmitting electromagnetic radiation, suchas Ul-lF television signals, is that in order to produce a concentratedradiation pattern necessary to obtain reasonable range, complex andexpensive antenna constructions are required. Usually such antennasproduce nulls at locations remote from the antenna but within the signalrange.

Accordingly, the principal object of the present invention is to providea simple, economical construction which achieves improved transmissionrange, in selected or all directions, while producing uniform radiationdistribution throughout the transmission pattern.

Briefly, the invention comprises a central hollow support member towhich are attached at least one pair of space frustoconical reflectorelements. Slots are provided in the support member extending between thereflector elements. A central conductor is positioned within the hollowsupport member, this conductor carrying energy from the transmitter tothe antenna. Probes connected to respective slots couple energy from thecentral conductor to the support member, the latter serving as an energyradiator. By adjusting the probe positions, the radiation pattern of theantenna can be controlled.

The invention will be described in further detail by reference to theaccompanying drawings wherein:

FIG. 1 is a cross-sectional view of a preferred embodiment of theinvention, the probes being omitted for convenience of illustration; and

FIG. 2 is an enlarged fragmented view of a portion of the arrangementshown in FIG. 1 with representative probes included.

Referring now to the drawings, the invention will be described indetail. The principal support structure of the antenna is a hollowmember formed of conductive material. Ideally this member has aninternal diameter of approximately 0.4 the wavelength (A) of the carrierfrequency which the antenna is intended to transmit. For example, ifused as a transmitting antenna for UHF channel 20, which has awavelength of approximately 22 inches, the inside diameter of member 10would be 8.8 inches. With an inside diameter greater than 0.4 A, thehollow member begins to act as a waveguide, whereas below 0.4)., thepower handling capabilities of the antenna are reduced.

Frustoconical reflecting elements 12 and 14 are connected at oppositeends of support member 10. The sides of these elements should be atleast 1.0). in length and preferably are 1.5 A. The angle at which thesides of elements 12 and 14 intersect member 10 is a function of thebeam tilt required for the particular environment where the antenna isto be used.

Three pairs of spaced frustoconical reflecting elements are positionedalong member 10 between elements 12 and 14. These comprise pairedelements 16 and 18, 20 and 22, and 24 and 26. The distance betweenadjacent reflector elements, where they join support member 10, is0.5).. The sides of elements 16, 18, 20, 22, 24 and 26 are 1.0K inlength. Each pair of reflector elements are joined at their bases.

Vertically extending slots 28 are disposed at 90 intervals about supportmember 10 and extend between reflector elements 12-16, 18-20, 22-24 and26-14. These slots are approximately 0.5?t in length.

A central conductor 30 extends along the axis of hollow support member10 and is fixed with respect to member 10 by conventional insulatingmeans (not shown). The conductor 30 terminates approximately halfwaybetween reflector elements 12 and 16. The conductor 30 may be telescopedat its end to provide adjustability to compensate for inductive andcapacitive reactances thereby permitting matching to a transmission linefrom the transmitter. Conductor 30 serves as an inner conductor of acoaxial cable, the outer conductor being support member 10. The bottomof conductor 30 is joined through a connector 32 to the transmissionline 34 extending to the transmitter (not shown).

FIG. 2 illustrates the manner by which energy is coupled from centralconductor 30 to the support member 10 to be radiated thereby. Moreparticularly,,probes 36 (only an opposing pair of which are shown) areconnected between each slot 28 and the central conductor. ln theembodiment illustrated, one end of each probe is fixed to the supportmember 10 along slot 28, and the other probe end is spaced from thecentral conductor 30. With such an arrangement; the energy iscapacitively coupled from conductor 30 to the support member 10, and theamount of energy fed to each slot 28 can be controlled by varying theprobe to central conductor spacing, as by providing probes 36 withuniversal joints 38. By controlling the amount of energy supplied toeach slot, the desired radiation pattern can be established.

The positioning of the ends of probes 36 along the slots 28 also affectsthe radiation pattern. Inasmuch as the slots 28 are 0.5). in length,this represents a possibility of varying the phase of the signal coupledby each probe 36 an amount of 180. lt is apparent, therefore, thatmovement of the probe one-fourth of the length of slot 28 represents a45 phase shift of the signal. In the preferred embodiment of theinvention, adjacent probes are electrically displaced by This isaccomplished, for example, by connecting each of one opposing pair ofprobes a quarter of the slot length from the bottom of its respectiveslot and by joining each of the other opposing pair of probes onefourthof the length from the top of its respective slot.

in the illustrative embodiment probes 36 capacitively couple energy fromcentral conductor 30 to the radiator which comprises support member 10.However, energy can be directly coupled by joining opposite ends of theprobe to a slot 28 and conductor 30. Also three pair of reflectors arepositioned between elements 12 and 14 in the embodiment shown. However,a lesser number can be used with an attendant loss in gain of thesystem. More reflector pairs would increase the gain obtainable from thearrangement. The dimensions of the reflector sides, the centralconductor, the reflector spacing, etc., are illustrative only, and itwill be appreciated that certain variations can be made within thespirit of the invention as defined by the appended claims.

What is claimed is:

1. A transmission antenna comprising:

a hollow conductive support member;

a pair of spaced frustoconical reflector elements joined to said supportmember;

a central conductor within said support member; and

means electrically connecting said central conductor to the supportmember along individual slots in said member which extend between thereflector elements and which are disposed about the support member, saidconnecting means being adjustably connected to said slots in positionsto effect phase displacement of the energy supplied to each slot withrespect to that supplied to the remaining slots.

2. An antenna as set forth in claim 1, wherein said reflector elementsare spaced at their joinder to said support member by a distance equalto one-half the wavelength of the carrier frequency to be transmitted.

3. An antenna as set forth in claim 1, wherein the side of each of saidfrustoconical elements is equal in length to at least the wavelength ofthe carrier frequency to be transmitted.

4. An antenna as set forth in claim 1, further comprising at least oneadditional pair of frustoconical reflector elements interposed betweensaid first-mentioned pair of elements and spaced therefrom, eachadditional pair being joined at their bases.

5. An antenna as set forth in claim 4 wherein each of said reflectorelements is spaced from adjacent elements at the joinder of saidelements to the support member by a distance of one-half the wavelengthof the carrier frequency to be transmitted.

6. An antenna as set forth in claim 4, wherein the side of each of saidfrustoconical elements is equal in length to at least the wavelength ofthe carrier frequency to be transmitted.

7. An antenna as set forth in claim 5, wherein the side of each of saidfrustoconical elements is equal in length to at least the wavelength ofthe carrier frequency to be transmitted.

8. An antenna as set forth in claim 7, wherein the sides of thefirst-mentioned pair of reflector elements are equal in length to 1%times the wavelength of the carrier frequency to adjacent thereto.

10. An antenna as set forth in claim 8, wherein said slots extendbetween each element of said additional reflector element pair and theelement positioned in spaced relationship adjacent thereto.

1. A transmission antenna comprising: a hollow conductive supportmember; a pair of spaced frustoconical reflector elements joined to saidsupport member; a central conductor within said support member; andmeans electrically connecting said central conductor to the supportmember along individual slots in said member which extend between thereflector elements and which are disposed about the support member, saidconnecting means being adjustably connected to said slots in positionsto effect phase displacemenT of the energy supplied to each slot withrespect to that supplied to the remaining slots.
 2. An antenna as setforth in claim 1, wherein said reflector elements are spaced at theirjoinder to said support member by a distance equal to one-half thewavelength of the carrier frequency to be transmitted.
 3. An antenna asset forth in claim 1, wherein the side of each of said frustoconicalelements is equal in length to at least the wavelength of the carrierfrequency to be transmitted.
 4. An antenna as set forth in claim 1,further comprising at least one additional pair of frustoconicalreflector elements interposed between said first-mentioned pair ofelements and spaced therefrom, each additional pair being joined attheir bases.
 5. An antenna as set forth in claim 4 wherein each of saidreflector elements is spaced from adjacent elements at the joinder ofsaid elements to the support member by a distance of one-half thewavelength of the carrier frequency to be transmitted.
 6. An antenna asset forth in claim 4, wherein the side of each of said frustoconicalelements is equal in length to at least the wavelength of the carrierfrequency to be transmitted.
 7. An antenna as set forth in claim 5,wherein the side of each of said frustoconical elements is equal inlength to at least the wavelength of the carrier frequency to betransmitted.
 8. An antenna as set forth in claim 7, wherein the sides ofthe first-mentioned pair of reflector elements are equal in length to 11/2 times the wavelength of the carrier frequency to be transmitted. 9.An antenna as set forth in claim 4, wherein said slots extend betweeneach element of said additional reflector element pair and the elementpositioned in spaced relationship adjacent thereto.
 10. An antenna asset forth in claim 8, wherein said slots extend between each element ofsaid additional reflector element pair and the element positioned inspaced relationship adjacent thereto.